delta ground

[elect36]

where in the code does it talk about a delta ground. Does it have to be put in after so many amps of service.

 

[augie47]

Re: delta ground

(a) amomng other places

240.85 discusses circuit breaker ratings on a corner grounded delta

250.25 discusses grounding

(b) NO

 

[elect36]

Re: delta ground

We've got a 480v 1200 amp service coming in and i'm trying to find out if we have to put 3 ground rod's in a triangle bonded together or could we just use one ground rod. of course we would bond the building steel of course either way we go.

 

[petersonra]

Re: delta ground

the rules on grounding electrodes are reasonably clear. i don't recall any situation that requires 3 rods though.

 

[infinity]

Re: delta ground

Are you asking about 3 ground rods wired in a delta configuration or the grounding of a 3 wire delta system?

 

[elect36]

Re: delta ground

i guess i'm asking about 3 ground rods in a delta configuration. at what times is it a have to is what i'm trying to find out

 

[iwire]

Re: delta ground

The NEC never requires ground rods in a delta configuration.

An engineer might specify that is what they want done.

Basically all the NEC types of grounding electrodes are described in 250.52 and the installation of these electrodes are covered in 250.53.

 

[augie47]

Re: delta ground

 

[elect36]

Re: delta ground

I guess i'm trying to find out why delta grounds are so common as far as installing in 480v systems but there are not even in the code besides where it talks about useing more ground rods for less res. on your grounds.

 

[iwire]

Re: delta ground

Originally posted by elect36:
I guess i'm trying to find out why delta grounds are so common as far as installing in 480v systems

Common is a relative term.

I have been at this for 20+ years mostly in buildings with 480 volt services and have only installed one set of ground rods in a delta.

There are a few possibility's.

1) Local amendment requiring delta rods.

2) You work on electrical systems designed by the same engineering firm.

3) It is just a trade practice in your area, because "We always do it that way"

Any of these reasons are fine, delta rods are not going to hurt anything and the NEC allows as many 'extra' rods as you want.

 

[George Stolz]

Re: delta ground

Is a crystal embedded in the center of the pyramid?

Sorry, that just sounds bizarre. I suppose, in a lightning strike, it would give the lightning a broader target to hit?

 

[iwire]

Re: delta ground

Originally posted by georgestolz:
Is a crystal embedded in the center of the pyramid?

Yes but do not let that secret out.

Originally posted by georgestolz:
I suppose, in a lightning strike, it would give the lightning a broader target to hit?

[ August 08, 2005, 08:10 AM: Message edited by: iwire ]